The emake client failed to rename a temporary cache slot directory. The cache was not updated, and temporary data may have been left behind.
The final portion of the error message is provided by the operating system, and indicates what exactly went wrong.
The emake client maintains an “asset directory”, which provides a memory of past builds to help future builds. Certain subdirectories of the asset directory correspond to cache “slots” used by Parse Avoidance and JobCache.
Emake wanted to update a cache slot, and created a temporary directory to accumulate the new state of that slot. Then it decided either to commit that change or to roll it back. But when it tried to rename that temporary directory, it failed to do so for some reason other than that the target pathname already exists.
See the trailing portion of the error message for the specific error reported by the operation system.